ABSTRACT: Freshwater-dominated estuaries experience large fluctuations in their physical and chemical environments which may influence larval dispersal, settlement, and connectivity of populations with pelagic larval stages. We used settlement patterns and natural tagging along with numerical hydrodynamic model results to assess settlement and connectivity among oysters across the freshwater-dominated Mobile Bay-eastern Mississippi Sound (MB-EMS) system. Specifically, we (1) tested how freshwater inputs and associated environmental attributes influenced settlement patterns during high and low discharge conditions in 2014 and 2016, respectively, and (2) analyzed trace element (TE) ratios incorporated into multiple shell types (larval and settled shell of spat and adult shells) to determine if shells collected in situ incorporate temporally stable site-specific signatures. We also assessed if TE ratios compared between adult (TE natal signature proxy) and larval shells could infer connectivity. Larval settlement was 4× higher during low discharge than during high discharge when oyster larvae only settled in higher salinity regions (EMS). Spat and adult shells incorporated site-specific TE ratios that varied from weeks to months. Connectivity results (May-June 2016 only) suggest that EMS is an important larval source to EMS and lower MB. While we were able to infer probable connectivity patterns using adult and larval shells, more study is needed to assess the utility of adult shells as proxies for natal-location TE signatures. Results provide a baseline for measuring future larval connectivity and adult distribution changes in the MB-EMS system. Biological and geochemical data demonstrate the potential to identify environmental attributes that spatiotemporally mediate settlement and connectivity in dynamic systems.

中文翻译：

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使用聚落模式和地球化学标记来测试东部牡蛎 Crassostrea virginica 的种群连通性

摘要：以淡水为主的河口在其物理和化学环境中经历了巨大的波动，这可能会影响具有远洋幼虫阶段的种群的幼虫扩散、定居和连通性。我们使用沉降模式和自然标记以及数值水动力模型结果来评估以淡水为主的莫比尔湾 - 密西西比东部海湾 (MB-EMS) 系统中牡蛎之间的沉降和连通性。具体而言，我们 (1) 分别测试了 2014 年和 2016 年淡水输入和相关环境属性如何影响高排放和低排放条件下的沉降模式，以及 (2) 分析了多种贝壳类型（幼虫和沉降）中的微量元素 (TE) 比率。贝壳和成虫壳）以确定是否在原地收集贝壳结合时间稳定的特定于站点的签名。我们还评估了成虫（TE 出生特征代理）和幼虫壳之间的 TE 比率是否可以推断连通性。当牡蛎幼虫仅在高盐度区域 (EMS) 定居时，低排放期间的幼虫沉降比高排放期间高 4 倍。卵和成虫壳结合了特定地点的 TE 比率，从数周到数月不等。连通性结果（仅限 2016 年 5 月至 6 月）表明 EMS 是 EMS 和较低 MB 的重要幼虫来源。虽然我们能够使用成虫和幼虫壳推断可能的连接模式，但需要更多的研究来评估成虫壳作为出生位置 TE 签名代理的效用。结果为测量 MB-EMS 系统中未来的幼虫连通性和成虫分布变化提供了基线。